1. Field of the Invention
The present invention relates to a circuit device, a method for manufacturing a circuit device, and a semiconductor module.
2. Description of the Related Art
In recent years, along with the on-going downsizing and functional sophistication of electronic devices, there has been an ever-growing demand for smaller circuit devices to be incorporated into electronic devices. One of known ways to meet such a demand is to narrow the pitch of external connection electrodes of a circuit device. But because of the size of solder bumps themselves used as the electrodes and the formation of bridges at soldering, there has existed a limit to the downsizing by narrowing the pitch of the external connection electrodes of a circuit device. For further downsizing of a circuit device, therefore, there is a technology conceived for rearrangement of external connection electrodes by forming a rewiring for a circuit device.
In such a technology, copper rewiring, electrode terminal forming and resin sealing are executed in a wafer level and then a wafer-level packaging (hereinafter referred to as “WLP”) is carried out in a chip state. For example, in a known WLP method, metal posts for element electrodes are formed by electroplating using a conductive metal such as copper or gold.
An electrolytic plating of copper, which is a kind of electroplating as mentioned above, is generally performed in a copper sulfate bath, and a soluble phosphorus-containing copper is used as an anode. When a phosphorus-containing copper anode is used, a black film composed of copper phosphide, copper chloride or the like is formed on the surface of the anode by the electrolysis, with the result that the generation of metallic copper or oxidized copper due to a disproportionation reaction of monovalent copper and the generation of particles can be suppressed.
However, when the phosphorus-containing copper anode dissolves, not only copper but also phosphorus solves out into the liquid, so that the plating solution gets contaminated with phosphorus, and the phosphorus codeposits in a plating film. As a result, the copper posts formed by this electrolytic plating has an increased degree of hardness because of the phosphorus contained as impurities, and thus they can present a problem of lowered connection reliability under stresses.